Atherosclerosis is a disease of the blood vessel wall that causes heart attacks, strokes, and loss of limbs. Despite major advances in medical and surgical management, atherosclerosis still causes significant morbidity and mortality. The impact of atherosclerosis on the health of the American people is expected to increase in the coming decades due to aging of the population and the consequences of the current obesity/diabetes epidemic among the young (diabetes is a major risk factor for atherosclerosis). The broad, long-term objective of this project is to decrease the morbidity and mortality of atherosclerosis by further clarifying its molecular and cellular pathogenesis, and by illuminating new targets for anti-atherosclerosis therapies. Atherosclerosis causes narrowing of blood vessels that restricts blood flow, precipitates chest and leg pains, and limits physical activity. However the major clinical events associated with atherosclerosis-heart attacks and strokes-are caused primarily by physical disruption or rupture of atherosclerotic plaques with consequent formation of blood clots that either completely block blood vessels or break free and block vessels downstream of the site of plaque rupture. Plaque rupture is thought to result from digestion of plaque proteins by enzymes known as proteases, which weakens plaque structural integrity and leads to rupture. However, this process is poorly understood and is not yet a target of any specific drug therapy. This project aims to unravel the molecular mechanisms through which proteases cause plaque rupture. There are two specific aims: Aim 1 uses blood vessels from genetically modified mice that were developed in our laboratory as an animal model of plaque rupture and Aim 2 uses human plaque tissue. Both aims use powerful new techniques to measure proteins, detect the digestion of proteins, and clarify physiologically meaningful relationships among the proteins. We will use these novel techniques to investigate the pathogenesis of plaque rupture in both the animal model and in human plaque tissue. We hope to identify new molecular targets for therapies that prevent plaque rupture. Moreover, data generated in the two aims will permit an objective assessment of the relevance of the mouse model to human plaque rupture. Therefore, these studies may validate a useful animal model of a common, clinically important, and poorly understood human disease. Accomplishment of our aims will help clarify the mechanisms through which atherosclerotic plaques rupture. Insights from our experiments may be useful in developing new therapies that prevent heart attacks and strokes.